degree, on those toward the north. It has previously been pointed out that almost all of the 

 scouting conditions classified as poor were encountered on runs toward the east and the highest 

 proportion of good conditions was found on the runs towards the west. Since the weather was 

 quite steady, we have no way of sepzirating a possible Doppler effect fronn the weather effect with 

 these data. 



But we do have direct observations on the schools, which frequently moved considerable 

 distances while they were being observed from the ship. It is reasonable to assume that any 

 collective migration of these schools would be evident in the average movennent of the individual 

 schools during the 5 to 15 minutes for which they were watched. (It will be recalled that when 

 schools were sighted, a minute-by-minute record of the ship's course and the relative bearing 

 and distance of the school was maintained. This permits reconstructing a track chart of the 

 school while it was under observation, though it is subject to some inaccuracies due to the prob- 

 lems of estimating distance. ) When the movements of these schools during the first 10 minutes 

 of observation are plotted, it is found that less than half of them show definite movement. Usually 

 the schools were nnilling about in one place, but at tin-ies they were moving and sometimes at 

 speeds of 10 to 15 knots. When we plot the movement of the schools which were seen to move 

 during a 10-minute period on all runs where the relative nunnbers of schools suggest the Doppler 

 effect (fig. 8), we find that the movement of the schools is almost a random one except on the 

 south arm of Area II in April, where most of the schools were moving southwesterly, on the east 

 emd the west arms of Area I in June, where they were moving westerly, and on the west arm of 

 Area IV, cruise 13, where they were moving northerly. Since the apparent Doppler effect sug- 

 gests a northeasterly movement and there is not a single instance of the concerted movement of 

 the schools while under observation substantiating this, we conclude that the apparent Doppler 

 effect is due entirely to weather and to the inevitable fluctuations of rather small numbers. 



The plots of figure 8 do suggest that at tinnes the movement of schools is concerted rather 

 than random, ajid this i:riay be further evidence of the tendency of schools to vacate or appear in 

 linnited localities. 



ABUNDANCE OF SCHOOLS IN RELATION TO LAND 

 AND TO THE FISHING AREA OF THE FLEET 



The Hawaiian skipjack fleet habitually operates within 20 miles of land and from 1948 to 

 1952 took 74. 5 percent of its catch in that zone (fig. 9). However, this does not meaji that the 

 vessels operate within 20 miles of port because some may range nnuch farther by operating along 

 other than their honne islands. Since the fishermen can be expected to know where the fish are 

 easiest to locate and can easily range 100 miles or more from land, the fact that most of the 

 catch came from within 20 miles might mean that skipjack are more abundant in this zone. More- 

 over, such abundance would be expected because of general observations that fish of many species 

 are more abundant near the reef. 



However, during our spring scouting more tuna schools per day were seen outside the zone 

 extending to 19 miles from shore (table 12). They were nnost abundant in the zone from 20 to 39 

 miles from shore, but to the limit of scouting, about 300 miles south of Oahu, they remained 

 slightly more abundant than in the inshore zone during most cruises. These small differences are 

 probably not significant, because much of the inshore scouting was performed on runs to hydro- 

 graphic stations or while on other missions when scouting was incidental. Furthermore, the areas 

 scouted were mostly between Oahu and Maui, or north and south of these islands. This area is 

 near the center of the fishery but is not representative of the entire fishing area in the zones 

 specified. We consider the data to indicate that the schools were nearly randomly distributed in 

 the area scouted but with local changes as indicated by the scarcity of schools in Area III in June, 

 2tnd with a shift in relative abundance between the north and south sides of the islands. 



After the discovery that the schools were abundant beyond the customary range of the 

 fleet and probably beyond the range of our spring scouting, we planned our fall scouting to en- 

 compass two larger sectors, one northeast and one southwest of Oahu (figs. 3 and 10). In these 

 sectors scouting was done out to 350 nniles southwest and to 2 30 miles northeast of Oahu. On all 

 three of the cruises, with the exception of one station, the schools were about equally abundant 



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